Pulse oximetry is used to measure the arterial oxygen saturation of hemoglobin (SpO2) and pulse rate of a patient. Measurement of these characteristics is accomplished by use of a non-invasive sensor which scatters red and infrared lights through a portion of the patient's tissue where arterial blood perfuses the tissue. The sensor then senses the absorption of light photoelectrically by the tissue. The differential amounts of red and infrared light absorbed are then used to calculate the percentage of hemoglobin in the arterial blood that is saturated with oxygen.
Pulse oximetry is commonly used as a monitoring device in the emergency departments, intensive care units, observational units, and operating rooms. Most pulse oximeter probes are designed for prolonged, continuous monitoring of the SpO2 and pulse rate of a patient. These probes are generally shaped as a clip for the finger or toe, or for infant using adhesive tapes for wrapping around the foot. For spot check of SpO2 or for the purpose of screening, using disposable probes is time consuming and not cost effective.
Congenital heart disease (CHD) affects 8 per 1,000 live-born infants and is one of the most common and serious types of birth defect. If diagnosed early, CHD can be managed with successful surgical repair or palliation for the majority of infants. A missed or delayed diagnosis can be life threatening or result in long-term morbidities for these infants. Current clinical practice for detecting CHD in newborns relies on a clinician performing a physical examination before the child's routine discharge from the nursery. A significant number of newborns with CHD are missed by routine physical examination.
In recent years, health care professionals have found pulse oximetry an important screening tool to aid clinical examination for detecting some severe forms of CHD. In a 2007 survey of 1,086 pediatric cardiologists, the majority of respondents support a mandate for universal screening by pulse oximetry before newborn discharge. In 2009, the American Heart Association and American Academy of Pediatrics jointly issued a scientific statement recommending routine pulse oximetry screening on the foot of asymptomatic newborns after 24 hours of life, but before hospital discharge.
The commonly used pulse oximetry sensors require attachment to the fingers or toes. In infants and neonates, the fingers and toes are too small for the clip-type of pulse oximetry sensor commonly used in older children and adults. Commonly used approaches include taping the pulse oximetry sensor in place on the finger/toe or hand/foot by adhesives or by Velcro. These sensors are generally single-use therefore adds substantial expenses to the universal screening of all newborn at hospital discharge. Taping a pulse oximetry sensor on an infant's toe or foot takes a considerable amount of time, which adds difficulty to screen a large number of newborns. Furthermore, the taping the pulse oximetry sensors on the toe or the foot is prone to motion artifacts, and signal interferences from ambient lights, which are less than ideal to be used in a setting of newborn screening. To summarize, the current pulse oximetry sensors cannot be used for newborn CHD screening because the single-use sensors add to the cost, takes a significant amount of time to place the sensors, and are prone to artifacts from motion and ambient light.
Kiani (US 2008/0071155 A1) teaches an invention of a congenital heart disease monitor using a pulse oximeter. The pulse oximeter uses conventional finger or wrap around probes to measure SpO2 from upper and lower extremities.
Mannheimer (U.S. Pat. No. 5,842,982) teaches an improved infant/neonatal pulse oximeter sensor that attaches to an infant's foot. A pad conforms to the heel of an infant, with the light emitter and a detector being mounted below the achilles tendon and below the calcaneus bone. The heel pad can be held in place with a stretchable sock.
Jackson III (US 2002/0133067 A1) discloses an invention of a SIDS warning device by a pulse oximeter mounted in a woven foot wrap. This device uses a low-powered transmitter to transmit readings to a remote monitoring unit. The wrapping is made of an opaque elastic material that secure not only around the arch and ball area of the infant's foot, but also around the ankle. The pulse oximeter will be placed in the wrap on the dorsal and plantar area near the arch of the infant's foot.
Pulse oximter probes to be used at other parts of the body have been proposed by other inventers. Melker et al (US 2004/0260161 A1) teaches a pulse oximeter probe to be used on the lip or cheek. Melker et al (WO 2005/065540 A1) also teaches a pulse oximeter probe to be used on the nose. Shepard et al (US 2002/0028990 A1) teaches a pulse oximeter probe to be used in the posterior pharynx. Although these pulse oximeter probes may be useful for patient monitoring, they cannot be used on newborns. Furthermore, the American Academy of Pediatrics specifically recommends the pulse oximetry to be performed on the foot for the purpose of screening for critical congenital heart disease.